There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

A convention is held where all the big logicians are summoned. The master places a band on everyone's forehead. Now all of them can see others bands but can't see his own. Then they are told that there are different colours of bands. All the logicians sit in circle and they are further explained that a bell will ring at regular intervals. The moment when a logician knew the colour of band on his forehead, he will leave at the next bell. If anyone leaves at the wrong bell, he will be disqualified.

The master assures the logicians that the puzzle will not be impossible for anyone of them. How will the logicians manage ?

A man who was outside in the rain without an umbrella or hat didn’t get a single hair on his head wet. Why?

There is an ancient kingdom where every married woman keeps information regarding the fidelity of other men. However, what they don't know is the fidelity of their own husbands. Also, there is an ancient belief that they don't tell each other about the fidelity of their husbands.

On a certain day, the queen of the kingdom declares that she has identified at least one unfaithful man in the kingdom. She allows the wives to identify and gives them authority to kill their husbands if they are unfaithful at midnight.

How will the wives manage it?

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

Find The Missing Number In the Sequence.
6 25 64 ? 32 1

What is the fastest way to double your money?

No matter how little or how much you use me, you change me every month. What am I?